The US space agency said there was a 60 percent chance that weather conditions would be favorable for the launch from Florida's Kennedy Space Center.

The launch is slated for 11:56 pm Saturday (0356 GMT Sunday), NASA said.

The decision to delay the launch of the second Mars Expedition Rover, dubbed Opportunity, had been made following an inspection of the Delta II rocket to be used in the blast off, the US space agency said.

The delay was deemed necessary to allow the rocket's manufacturer, Boeing, to make some modifications.

The probe is scheduled to land on January 25, 2004 in an area of Mars known as the Meridiani Planum.

The first probe, named Spirit, blasted off from Florida on June 10 and is expected to land in the Red Planet's Gusev crater on January 3, 2004.

SPACE.WIRE